Steam generation system

ABSTRACT

There is provided an efficient steam generation system capable of reducing a temperature difference in heat to be drawn by a heat pump. A first heat pump ( 2 ) includes a first evaporator ( 7 ) and a second evaporator ( 8 ). A second heat pump ( 3 ) is connected to the first heat pump ( 2 ) via an uppermost condenser ( 10 ) serving as the first evaporator ( 7 ). A heat source fluid is passed through a second evaporator ( 8 ) of the first heat pump ( 2 ) and an evaporator ( 12 ) of the second heat pump ( 3 ) in sequence. Then, steam is generated by application of heat to water in a condenser ( 5 ) of the first heat pump ( 2 ).

TECHNICAL FIELD

The present invention relates to a steam generation system forgenerating steam by means of a heat pump. This application claimspriority on Patent Application No. 2011-079370 filed in Japan on Mar.31, 2011, the contents of which are hereby incorporated by reference.

BACKGROUND ART

As disclosed in Patent Literature 1, heretofore, there has been known aheat pump in which an evaporator draws heat from a hot drain or the likeand a condenser generates steam by application of the heat to water.

As disclosed in Patent Literature 2, moreover, there has been proposed asystem including a multiple-stage heat pump in which heat pumps arevertically disposed. Herein, feed water is passed through a heatexchanger (serving as a condenser of the lower heat pump and anevaporator of the upper heat pump) that connects between the upper andlower heat pumps, so that heat is applied to the feed water. Then, steamis taken out from a condenser of the uppermost heat pump.

As disclosed in Patent Literature 3, further, there has also beenproposed an apparatus including heat pumps disposed from side to side inparallel. Herein, water is passed through condensers of the respectiveheat pumps in sequence, thereby obtaining hot water.

-   Patent Literature 1: JP 58-40451 A (FIG. 2)-   Patent Literature 2: JP 2006-348876 A (FIGS. 1, 2)-   Patent Literature 3: JP 60-23669 U (FIG. 2)

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

According to the invention disclosed in Patent Literature 1, the heatpump is a single-stage heat pump. However, the efficiency of the heatpump is poor because there is a large temperature difference in heat tobe drawn, i.e., a large temperature difference between the evaporatorside and the condenser side.

According to the invention disclosed in Patent Literature 2, the heatpump is a multiple-stage heat pump in which heat pumps are verticallydisposed. However, in the case where heat is drawn from only theevaporator of the lowermost heat pump, there is a large temperaturedifference in heat to be drawn as a whole of the heat pumps, as in theinvention disclosed in Patent Literature 1. Therefore, the improvementin efficiency of the heat pump is restricted.

According to the invention disclosed in Patent Literature 3, the heatpumps are disposed from side to side in parallel. However, in the casewhere the right and left heat pumps have an identical configuration andheat is drawn from only the evaporator of the lowermost heat pump, thereis a large temperature difference in heat to be drawn, as in theinvention disclosed in Patent Literature 2. Therefore, the improvementin efficiency of the heat pump is restricted.

Further, in a case where a heat source fluid is hot water, exhaust gasor the like and undergoes a decrease in temperature while applying heat(sensible heat) to the heat pump, when the heat source fluid is merelypassed through the heat pumps which are the same in configuration aseach other and are disposed in parallel, the temperature of the heatsource fluid is decreased in the downstream heat pump. Therefore, thereis a necessity to take the decrease in temperature into consideration.

It is one object of the present invention to reduce a temperaturedifference in heat to be drawn as a whole of a system, thereby improvingthe efficiency of the system. It is another object of the presentinvention to provide a steam generation system capable of dealing with adecrease in temperature caused in a case where a heat source fluidapplies sensible heat to a heat pump.

Means for Solving the Problems

The present invention has been devised to solve the problems describedabove. An invention of claim 1 is a steam generation system including: asingle-stage or multiple-stage first heat pump in which at least thelowermost heat pump includes a first evaporator and a second evaporator;and a single-stage or multiple-stage second heat pump connected to thefirst heat pump via a condenser of the uppermost heat pump, thecondenser serving as the first evaporator of the lowermost heat pump,wherein a heat source fluid is passed through the second evaporator ofthe first heat pump and an evaporator of the lowermost heat pump in thesecond heat pump in sequence, and steam is generated by application ofheat to water in a condenser of the uppermost heat pump in the firstheat pump.

According to the invention of claim 1, heat is drawn from the secondevaporator of the first heat pump and the evaporator of the lowermostheat pump in the second heat pump, so that steam can be generated in thecondenser of the uppermost heat pump in the first heat pump. Herein, theheat source fluid is passed through the second evaporator of the firstheat pump, and then is passed through the evaporator of the lowermostheat pump in the second heat pump. Thus, the second heat pump is capableof making up the heat drawn from the heat source fluid in the secondevaporator of the first heat pump, thereby drawing heat again from theheat source fluid passed through the second evaporator. Moreover, thefirst heat pump is capable of reducing a temperature difference in heatto be drawn, restraining power consumption in the compressor inaccordance with the reduction, and improving the efficiency of the steamgeneration system.

An invention of claim 2 is the steam generation system of claim 1,wherein the second heat pump is a single-stage heat pump, heat is drawnfrom the heat source fluid passed through the second evaporator of thefirst heat pump and the evaporator of the lowermost heat pump in thesecond heat pump in sequence, and steam is generated by application ofthe heat to water in the condenser of the uppermost heat pump in thefirst heat pump.

According to the invention of claim 2, the steam generation systemincludes the single-stage or multiple-stage first heat pump and thesingle-stage second heat pump. Herein, the heat source fluid is passedthrough the second evaporator of the first heat pump, and the evaporatorof the lowermost heat pump in the second heat pump in sequence. Thus,steam can be generated in the condenser of the uppermost heat pump inthe first heat pump.

An invention of claim 3 is the steam generation system of claim 1 or 2,wherein the first heat pump is a multiple-stage heat pump in which someof or all of the heat pumps each include the first evaporator and thesecond evaporator as an evaporator, each of the first evaporatorsconnects between the vertically adjoining heat pumps, and the heatsource fluid is passed through the respective second evaporators insequence from the upper heat pump toward the lower heat pump.

According to the invention of claim 3, the steam generation systemincludes three or more heat pumps as a whole. Herein, the heat sourcefluid is passed through the respective second evaporators of the firstheat pump in sequence from the upper heat pump toward the lower heatpump, and then is passed through the evaporator of the lowermost heatpump in the second heat pump. Thus, steam can be generated byapplication of heat to water in the condenser of the uppermost heat pumpin the first heat pump.

An invention of claim 4 is the steam generation system of claim 3,wherein the heat pumps in the multiple-stage first heat pump eachinclude the first evaporator and the second evaporator as an evaporator.

According to the invention of claim 4, the heat source fluid is passedthrough the second evaporator of each heat pump in the first heat pump,and then is passed through the evaporator of the lowermost heat pump inthe second heat pump. Thus, steam can be generated in such a manner thatheat is drawn with good efficiency with a simple configuration.

An invention of claim 5 is the steam generation system of any one ofclaims 1 to 4, wherein in the heat pump including the first and secondevaporators in the single-stage or multiple-stage first heat pump, thefirst evaporator and the second evaporator are provided in series or inparallel on a refrigerant channel from an expansion valve to acompressor, or a first expansion valve and the first evaporator areprovided in parallel with a second expansion valve and the secondevaporator on a refrigerant channel from a condenser to a compressor.

According to the invention of claim 5, the first evaporator and thesecond evaporator are provided in series or in parallel. Alternatively,the first expansion valve and the first evaporator are provided inparallel with the second expansion valve and the second evaporator.Then, heat is drawn in the second evaporator of the first heat pump andthe evaporator of the lowermost heat pump in the second heat pump. Thus,steam can be generated in the condenser of the uppermost heat pump inthe first heat pump.

An invention of claim 6 is the steam generation system of any one ofclaims 1 to 5, wherein the first heat pump and the second heat pump areconnected in accordance with one of the following relations (a) to (c):(a) an indirect heat exchanger is provided for receiving a refrigerantfrom a compressor of the second heat pump and a refrigerant from anexpansion valve of the first heat pump to perform heat exchange withoutmixing both the refrigerants, and serves as the condenser of the secondheat pump and the first evaporator of the first heat pump; (b) anintermediate cooler is provided for receiving a refrigerant from acompressor of the second heat pump and a refrigerant from an expansionvalve of the first heat pump to perform heat exchange by bringing boththe refrigerants into direct contact with each other, and serves as thecondenser of the second heat pump and the first evaporator of the firstheat pump; and (c) an intermediate cooler is provided for receiving arefrigerant from a compressor of the second heat pump and a refrigerantfrom an expansion valve of the first heat pump to perform heat exchangeby bringing both the refrigerants into direct contact with each otherand also to perform heat exchange without mixing both the refrigerantswith a refrigerant to be supplied from the condenser of the first heatpump to the expansion valve of the second heat pump without being passedthrough the expansion valve, and serves as the condenser of the secondheat pump and the first evaporator of the first heat pump.

According to the invention of claim 6, the steam generation system canbe configured in such a manner that the first heat pump and the secondheat pump are connected to each other via the indirect heat exchanger orthe intermediate cooler.

An invention of claim 7 is the steam generation system of any one ofclaims 1 to 6, wherein when the first heat pump and/or the second heatpump are/is a multiple-stage heat pump, the adjoining heat pumps areconnected in accordance with one of the following relations (a) to (c):(a) an indirect heat exchanger is provided for receiving a refrigerantfrom a compressor of the lower heat pump and a refrigerant from anexpansion valve of the upper heat pump to perform heat exchange withoutmixing both the refrigerants, and serves as a condenser of the lowerheat pump and an evaporator of the upper heat pump; (b) an intermediatecooler is provided for receiving a refrigerant from a compressor of thelower heat pump and a refrigerant from an expansion valve of the upperheat pump to perform heat exchange by bringing both the refrigerantsinto direct contact with each other, and serves as the condenser of thelower heat pump and the evaporator of the upper heat pump; and (c) anintermediate cooler is provided for receiving a refrigerant from acompressor of the lower heat pump and a refrigerant from an expansionvalve of the upper heat pump to perform heat exchange by bringing boththe refrigerants into direct contact with each other and also to performheat exchange without mixing both the refrigerants with a refrigerant tobe supplied from the condenser of the upper heat pump to the expansionvalve of the lower heat pump without being passed through the expansionvalve, and serves as the condenser of the lower heat pump and theevaporator of the upper heat pump.

According to the invention of claim 7, the first heat pump and/or thesecond heat pump can be configured with a multiple-stage heat pump.Moreover, the steam generation system can be configured in such a mannerthat the adjoining heat pumps are connected to each other via theindirect heat exchanger or the intermediate cooler.

An invention of claim 8 is the steam generation system of claim 6,wherein when the first heat pump and the second heat pump are connectedin accordance with the relation (b) in claim 6, the refrigerant from thecompressor of the second heat pump is supplied to a refrigerant channelfrom the intermediate cooler to the compressor, in place of or inaddition to the supply to the intermediate cooler.

According to the invention of claim 8, the refrigerant from thecompressor of the second heat pump is prevented from being supplied tothe intermediate cooler. Thus, the heat exchanger that constitutes theintermediate cooler can be made small. Moreover, the invention of claim8 is capable of preventing lubricant for the compressor of the secondheat pump from retaining in the intermediate cooler and is also capableof preventing the compressor of the first heat pump from being out ofoil.

An invention of claim 9 is the steam generation system of claim 6,wherein when the first heat pump and the second heat pump are connectedin accordance with the relation (c) in claim 6, the refrigerant from thecompressor of the second heat pump is supplied to a refrigerant channelfrom the intermediate cooler to the compressor in the first heat pump,or a refrigerant channel from the expansion valve to the intermediatecooler or compressor, in place of or in addition to the supply to theintermediate cooler.

According to the invention of claim 9, the refrigerant from thecompressor of the second heat pump is prevented from being supplied tothe intermediate cooler. Thus, the heat exchanger that constitutes theintermediate cooler can be made small.

An invention of claim 10 is the steam generation system of claim 6,further including: a separator for separating the refrigerant from theexpansion valve of the first heat pump into a vapor phase and a liquidphase when the first heat pump and the second heat pump are connected inaccordance with the relation (c) in claim 6, wherein the vapor-phaserefrigerant separated by the separator is supplied to a refrigerantchannel from the second evaporator to the compressor.

According to the invention of claim 10, the separator is provided forpreventing the vapor-phase refrigerant from being supplied to theintermediate cooler and/or the second evaporator. Therefore, the heatexchanger that constitutes these components can be made small.

An invention of claim 11 is the steam generation system of any one ofclaims 1 to 10, further including at least one of: (a) a first sub-heatexchanger for performing heat exchange between the water and therefrigerant from the condenser to the expansion valve in the uppermostheat pump of the first heat pump; (b) a second sub-heat exchanger forperforming heat exchange between the heat source fluid and therefrigerant from the evaporator to the compressor in the lowermost heatpump of the second heat pump; (c) a third sub-heat exchanger forperforming heat exchange between the refrigerant from the expansionvalve to the compressor in the lowermost heat pump of the first heatpump and the refrigerant from the compressor to the first evaporator inthe second heat pump, in a case where the first evaporator is anindirect heat exchanger; and (d) a fourth sub-heat exchanger forperforming heat exchange between the heat source fluid and therefrigerant from the expansion valve to the compressor in the lowermostheat pump of the first heat pump, wherein with regard to order ofdistribution of the water and steam to the condenser of the uppermostheat pump in the first heat pump, and the first sub-heat exchanger inthe case where the first sub-heat exchanger is provided, the firstsub-heat exchanger is provided on the upstream side in the case wherethe first sub-heat exchanger is provided, with regard to order ofdistribution of the heat source fluid to the second evaporator of thefirst heat pump, the fourth sub-heat exchanger in the case where thefourth sub-heat exchanger is provided, the evaporator of the lowermostheat pump in the second heat pump, and the second sub-heat exchanger inthe case where the second sub-heat exchanger is provided, the evaporatorof the lowermost heat pump in the second heat pump is provided on thedownstream side, and with regard to order of distribution of therefrigerant to the first evaporator of the first heat pump, the thirdsub-heat exchanger in the case where the third sub-heat exchanger isprovided, the second evaporator of the first heat pump, and the fourthsub-heat exchanger in the case where the fourth sub-heat exchanger isprovided, the first evaporator and the second evaporator are provided onthe upstream side of the third sub-heat exchanger and the fourthsub-heat exchanger.

According to the invention of claim 11, the first sub-heat exchanger isused as a refrigerant supercooler, the second sub-heat exchanger is usedas a refrigerant superheater, the fourth sub-heat exchanger is used as arefrigerant superheater, and the third sub-heat exchanger is provided asappropriate. Thus, the efficiency of the steam generation system can beimproved.

An invention of claim 12 is the steam generation system of any one ofclaims 1 to 11, wherein the heat source fluid is a drain from asteam-utilizing facility.

According to the invention of claim 12, steam can be generated byrecovering heat from the drain discharged from the steam-utilizingfacility.

Effects of the Invention

According to the present invention, it is possible to reduce atemperature difference in heat to be drawn as a whole of a system,thereby improving the efficiency of the system. It is also possible todeal with a decrease in temperature caused in a case where a heat sourcefluid applies sensible heat to a heat pump.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a steam generation systemaccording to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating order of distribution of a heat sourcefluid to a fourth sub-heat exchanger, a second evaporator of a firstheat pump, a second sub-heat exchanger, and an evaporator of a secondheat pump.

FIG. 3 is a diagram illustrating order of distribution of a refrigerantin the first heat pump to a first evaporator of the first heat pump, athird sub-heat exchanger, the second evaporator of the first heat pump,and the fourth sub-heat exchanger.

FIG. 4 is a graph illustrating a comparison between the steam generationsystem of the present invention and a conventionally well-knowntwo-stage heat pump in terms of a coefficient of performance.

FIG. 5 is a graph illustrating a comparison between the steam generationsystem of the present invention and the conventionally well-knowntwo-stage heat pump in terms of a compressor intake volume flow rate ineach of upper and lower heat pumps.

FIG. 6A is a T-S diagram illustrating an ideal cycle.

FIG. 6B is a T-S diagram of a conventionally well-known single-stageheat pump (inverse Carnot cycle).

FIG. 7 is a T-S diagram of the steam generation system according to thisembodiment.

FIG. 8 illustrates a case where the number of the heat pumps isincreased in FIG. 7.

FIG. 9 is a schematic diagram illustrating a steam generation systemaccording to a second embodiment of the present invention.

FIG. 10 is a schematic diagram illustrating a modification example ofthe steam generation system according to the second embodiment.

FIG. 11 is a schematic diagram illustrating a steam generation systemaccording to a third embodiment of the present invention.

FIG. 12 is a schematic diagram illustrating a modification example ofthe steam generation system according to the third embodiment.

FIG. 13 is a schematic diagram illustrating a steam generation systemaccording to a fourth embodiment of the present invention.

FIG. 14 is a diagram illustrating order of distribution of a refrigerantin a first heat pump to a first evaporator of the first heat pump, and athird sub-heat exchanger, and order of distribution of the refrigerantin the first heat pump to a second evaporator of the first heat pump,and a fourth sub-heat exchanger, in the fourth embodiment.

FIG. 15 is a schematic diagram illustrating a steam generation systemaccording to a fifth embodiment of the present invention.

FIG. 16 is a schematic diagram illustrating a modification example ofthe steam generation system according to the fifth embodiment.

FIG. 17 is a schematic diagram illustrating a steam generation systemaccording to a sixth embodiment of the present invention.

FIG. 18 is a schematic diagram illustrating a first modification exampleof the steam generation system according to the sixth embodiment.

FIG. 19 is a schematic diagram illustrating a second modificationexample of the steam generation system according to the sixthembodiment.

FIG. 20 is a diagram illustrating a combination of layout of a firstseparator, a second separator and a third separator.

FIG. 21 is a schematic diagram illustrating a steam generation systemaccording to a seventh embodiment of the present invention.

FIG. 22 is a schematic diagram illustrating a steam generation systemaccording to an eighth embodiment of the present invention.

FIG. 23 is a schematic diagram illustrating a first modification exampleof the steam generation system according to the eighth embodiment.

FIG. 24 is a schematic diagram illustrating a second modificationexample of the steam generation system according to the eighthembodiment.

FIG. 25 is a schematic diagram illustrating a steam generation systemaccording to a ninth embodiment of the present invention.

FIG. 26 is a schematic diagram illustrating a first modification exampleof the steam generation system according to the ninth embodiment.

FIG. 27 is a schematic diagram illustrating a second modificationexample of the steam generation system according to the ninthembodiment.

FIG. 28 is a diagram illustrating a combination of layout of a firstseparator and a second separator.

FIG. 29A is a schematic diagram illustrating one example of a steamgeneration system according to the present invention, the steamgeneration system including three or more heat pumps.

FIG. 29B is a T-S diagram in a case where a first heat pump is asingle-stage heat pump and a second heat pump is a two-stage heat pump.

FIG. 29C is a T-S diagram in a case where a first heat pump is amultiple-stage heat pump in which each heat pump includes a firstevaporator and a second evaporator and a second heat pump is asingle-stage heat pump.

FIG. 30 is a schematic diagram illustrating one example of a steamsystem using the steam generation system according to the firstembodiment.

FIG. 31 is a schematic diagram illustrating a modification example ofthe steam system illustrated in FIG. 30.

EXPLANATION OF REFERENCE NUMERALS

-   -   1 Steam generation system    -   2 First heat pump    -   3 Second heat pump    -   4 Compressor (of first heat pump)    -   5 Condenser (of first heat pump)    -   6 Expansion valve (of first heat pump)    -   7 First evaporator (of first heat pump)    -   8 Second evaporator (of first heat pump)    -   9 Compressor (of second heat pump)    -   10 Condenser (of second heat pump)    -   11 Expansion valve (of second heat pump)    -   12 Evaporator (of second heat pump)    -   13 Indirect heat exchanger    -   14 First sub-heat exchanger    -   15 Second sub-heat exchanger    -   16 Third sub-heat exchanger    -   17 Fourth sub-heat exchanger    -   18 Intermediate cooler    -   19 Intermediate cooler    -   22 Separator    -   27 Steam system    -   29 Steam-utilizing facility

PREFERRED MODE FOR CARRYING OUT THE INVENTION

A steam generation system of the present invention includes amultiple-stage heat pump. In the multiple-stage heat pump, some or allof the heat pumps excluding the lowermost heat pump each include a firstevaporator and a second evaporator. Each of the first evaporatorsconnects between the adjoining upper and lower heat pumps. A heat sourcefluid is passed through the respective second evaporators in sequencefrom the upper heat pump toward the lower heat pump. Steam is generatedby application of heat to water in a condenser of the uppermost heatpump.

Hereinafter, detailed description will be given of specific embodimentsof the present invention with reference to the drawings.

EMBODIMENTS First Embodiment

FIG. 1 is a schematic diagram illustrating a steam generation system 1according to a first embodiment of the present invention. The steamgeneration system 1 according to this embodiment includes a first heatpump 2 and a second heat pump 3.

The first heat pump 2 is of a steam compression type and is asingle-stage heat pump in this embodiment. Specifically, the first heatpump 2 includes a compressor 4, a condenser 5, an expansion valve 6, anevaporator 7 and an evaporator 8 which are sequentially and cyclicallyconnected to one another. Herein, the first heat pump 2 includes the twoevaporators, i.e., the first evaporator 7 and the second evaporator 8which are connected in series in this embodiment. That is, a refrigerantfrom the expansion valve 6 of the first heat pump 2 is passed throughthe first evaporator 7 and the second evaporator 8 in sequence (or inthe reverse order as will be described later), and then is fed to thecompressor 4.

The compressor 4 compresses the gaseous refrigerant to make thetemperature and pressure thereof high. The condenser 5 condenses andliquidizes the gaseous refrigerant from the compressor 4. The expansionvalve 6 allows the liquid refrigerant from the condenser 5 to passtherethrough, thereby decreasing the pressure and temperature of therefrigerant. The evaporators 7 and 8 evaporate the refrigerant from theexpansion valve 6.

Accordingly, the first heat pump 2 has the configuration that therefrigerant is vaporized by absorbing heat from the outside in theevaporators 7 and 8 and is condensed by dissipating heat into theoutside in the condenser 5. With this configuration, the first heat pump2 draws heat from the heat source fluid or the like in the evaporators 7and 8, and applies heat to water, thereby generating steam in thecondenser 5.

The heat source fluid (the heat source for each of the heat pumps 2 and3) is not particularly limited. The heat source fluid to be suitablyused herein is a fluid applying sensible heat to each of the heat pumps2 and 3, i.e., a fluid undergoing a decrease in temperature whileapplying heat to each of the heat pumps 2 and 3. Examples of the heatsource fluid may include a drain from a steam-utilizing facility,exhaust gas from a boiler, and the like.

Desirably, a circuit of the heat pump 2 may be provided with an oilseparator on the outlet side of the compressor 4, a liquid receiver onthe outlet side of the condenser 5, an accumulator on the inlet side ofthe compressor 4, or a liquid-gas heat exchanger performing heatexchange without mixing the refrigerant from the condenser 5 to theexpansion valve 6 with the refrigerant from the evaporators 7 and 8 tothe compressor 4. The similar things may hold true for the second heatpump 3 in addition to the first heat pump 2. In a case where each of thefirst heat pump 2 and the second heat pump 3 is configured with amultiple-stage heat pump, the similar things may hold true for each heatpump in the multiple-stage heat pump.

The second heat pump 3 is of a steam compression type and is asingle-stage heat pump in this embodiment. The second heat pump 3 isbasically similar in configuration to the first heat pump 2. That is,the second heat pump 3 includes a compressor 9, a condenser 10, anexpansion valve 11 and an evaporator 12 which are sequentially andcyclically connected to one another. Unlike the first heat pump 2,however, the second heat pump 3 does not necessarily include twoevaporators. The heat pump 3 draws heat from a heat source fluid in theevaporator 12, and applies heat to the refrigerant in the first heatpump 2 to condense the refrigerant in the condenser 10.

The first heat pump 2 and the second heat pump 3 are connected asfollows. That is, an indirect heat exchanger 13 is provided forreceiving the refrigerant from the compressor 9 of the second heat pump3 and the refrigerant from the expansion valve 6 of the first heat pump2 and performing heat exchange without mixing both the refrigerants. Theindirect heat exchanger 13 serves as the condenser 10 of the second heatpump 3 and the first evaporator 7 of the first heat pump 2. Therefrigerants in the respective heat pumps 2 and 3 may be the same as ordifferent from each other. The refrigerant to be used herein is notparticularly limited, and a suitable example thereof may include:hydrofluorocarbon (HFC) having four or more carbon atoms (e.g.,R-365mfc) or a mixture thereof with water and/or a fire extinguishingagent; alcohol (e.g., ethyl alcohol, methyl alcohol or trifluoroethanol(TFE)) or a mixture thereof with water and/or a fire extinguishingagent; or water (e.g., pure water or soft water).

The heat source fluid is passed through the second evaporator 8 of thefirst heat pump 2 and the evaporator 12 of the second heat pump 3;however, the detailed description thereof will be given later.Accordingly, the steam generation system 1 draws heat from the heatsource fluid in the evaporators 8 and 12, and applies the heat to water,thereby generating steam in the condenser 5 of the first heat pump 2.

The steam generation system 1 may include at least one of the followingvarious sub-heat exchangers 14 to 17 to be described below.

(a) The first sub-heat exchanger 14 is an indirect heat exchanger forperforming heat exchange between water and the refrigerant from thecondenser 5 to the expansion valve 6 in the first heat pump 2, andfunctions as a refrigerant supercooler of the heat pump 2.

(b) The second sub-heat exchanger 15 is an indirect heat exchanger forperforming heat exchange between the heat source fluid and therefrigerant from the evaporator 12 to the compressor 9 in the secondheat pump 3, and functions as a refrigerant superheater of the secondheat pump 3.

(c) The third sub-heat exchanger 16 is an indirect heat exchanger forperforming heat exchange between the refrigerant from the expansionvalve 6 to the compressor 4 in the first heat pump 2 and the refrigerantfrom the compressor 9 to the first evaporator 7 in the second heat pump3, in a case where the first evaporator 7 is the indirect heat exchanger13, and functions as a refrigerant superheater of the first heat pump 2.

(d) The fourth sub-heat exchanger 17 is an indirect heat exchanger forperforming heat exchange between the heat source fluid and therefrigerant from the expansion valve 6 to the compressor 4 in the firstheat pump 2, and functions as a refrigerant superheater of the firstheat pump 2.

Next, description will be given of a route of distribution of water andsteam.

Water is supplied to and then steam is derived from the condenser 5 ofthe first heat pump 2 and the first sub-heat exchanger 14 to be providedas desired. With regard to the order of distribution of the water andsteam, in the case where the first sub-heat exchanger 14 is provided,the first sub-heat exchanger 14 is provided on the upstream side of thecondenser 5 of the first heat pump 2. Typically, saturated steam isderived from the condenser 5 of the first heat pump 2. As illustrated inFIG. 1, the condensers 5 and 10 of the respective heat pumps 2 and 3 areprovided one by one. However, a plurality of heat exchangers may beprovided in series or in parallel.

Next, description will be given of a route of distribution of a heatsource fluid.

The second evaporator 8 of the first heat pump 2, the fourth sub-heatexchanger 17 to be provided as desired, the evaporator 12 of the secondheat pump 3 and the second sub-heat exchanger 15 to be provided asdesired are provided in appropriate order, and the heat source fluid ispassed therethrough. As the route of distribution of the heat sourcefluid, one of routes of distribution illustrated in FIG. 2 is employed.

FIG. 2 is a diagram illustrating the order of distribution of the heatsource fluid to the fourth sub-heat exchanger 17 to be provided asdesired, the second evaporator 8 of the first heat pump 2, the secondsub-heat exchanger 15 to be provided as desired, and the evaporator 12of the second heat pump 3. Numerals in FIG. 2 indicate the order ofdistribution to the respective heat exchangers 17, 8, 15 and 12, and “0”indicates that the relevant heat exchanger is not provided. The heatexchangers indicated by the same numeral are provided in parallel andcan be interchanged with each other. As illustrated in FIG. 2, theevaporators 8 and 12 of the respective heat pumps 2 and 3 are providedone by one. However, a plurality of heat exchangers may be provided inseries or in parallel.

Some specific examples will be described below. For example, “1”, “2”,“3” and “4” are shown in the first row. Herein, the fourth sub-heatexchanger 17 corresponds to “1”, the second evaporator 8 of the firstheat pump 2 corresponds to “2”, the second sub-heat exchanger 15corresponds to “3”, and the evaporator 12 of the second heat pump 3corresponds to “4”. In this case, the heat source fluid is passedthrough the fourth sub-heat exchanger 17, the second evaporator 8 of thefirst heat pump 2, the second sub-heat exchanger 15, and the evaporator12 of the second heat pump 3 in sequence.

Moreover, “1”, “2”, “1” and “3” are shown in the second row. Herein, thefourth sub-heat exchanger 17 corresponds to “1”, the second evaporator 8of the first heat pump 2 corresponds to “2”, the second sub-heatexchanger 15 corresponds to “1”, and the evaporator 12 of the secondheat pump 3 corresponds to “3”. In this case, the heat source fluid ispassed through the fourth sub-heat exchanger 17 and the second sub-heatexchanger 15 in parallel, and then is passed through the secondevaporator 8 of the first heat pump 2, and the evaporator 12 of thesecond heat pump 3 in sequence.

Further, “1”, “2”, “0” and “3” are shown in the fourth row. Herein, thefourth sub-heat exchanger 17 corresponds to “1”, the second evaporator 8of the first heat pump 2 corresponds to “2”, the second sub-heatexchanger 15 corresponds to “0”, and the evaporator 12 of the secondheat pump 3 corresponds to “3”. In this case, the second sub-heatexchanger 15 is not provided, and the heat source fluid is passedthrough the fourth sub-heat exchanger 17, and then is passed through thesecond evaporator 8 of the first heat pump 2, and the evaporator 12 ofthe second heat pump 3 in sequence.

In any order of distribution of the heat source fluid, basically, it ispreferred that the evaporator 12 of the second heat pump 3 is providedon the downstream side. In other words, the heat source fluid is passedthrough the second evaporator 8 of the first heat pump 2, and then ispassed through the evaporator 12 of the second heat pump 3.

FIG. 3 is a diagram illustrating the order of distribution of therefrigerant in the first heat pump 2 to the first evaporator 7 of thefirst heat pump 2, the third sub-heat exchanger 16 to be provided asdesired, the second evaporator 8 of the first heat pump 2, and thefourth sub-heat exchanger 17 to be provided as desired. Numerals in FIG.3 each indicate the order of distribution to the respective heatexchangers 7, 16, 8 and 17, and “0” indicates that the relevant heatexchanger is not provided. Moreover, the heat exchangers indicated bythe same numeral are provided in parallel.

Some specific examples will be described below. For example, “1”, “3”,“2” and “3” are shown in the first row. Herein, the first evaporator 7corresponds to “1”, the third sub-heat exchanger 16 corresponds to “3”,the second evaporator 8 corresponds to “2”, and the fourth sub-heatexchanger 17 corresponds to “3”. In this case, the refrigerant from theexpansion valve 6 of the first heat pump 2 is passed through the firstevaporator 7 and the second evaporator 8 in sequence, then is passedthrough the third sub-heat exchanger 16 and the fourth sub-heatexchanger 17 in parallel, and is fed to the compressor 4.

Moreover, “1”, “3”, “2” and “4” are shown in the second row. Herein, thefirst evaporator 7 corresponds to “1”, the third sub-heat exchanger 16corresponds to “3”, the second evaporator 8 corresponds to “2”, and thefourth sub-heat exchanger 17 corresponds to “4”. In this case, therefrigerant from the expansion valve 6 of the first heat pump 2 ispassed through the first evaporator 7, the second evaporator 8, thethird sub-heat exchanger 16 and the fourth sub-heat exchanger 17 insequence, and is fed to the compressor 4.

Further, “1”, “3”, “2” and “0” are shown in the fourth row. Herein, thefirst evaporator 7 corresponds to “1”, the third sub-heat exchanger 16corresponds to “3”, the second evaporator 8 corresponds to “2”, and thefourth sub-heat exchanger 17 corresponds to “0”. In this case, thefourth sub-heat exchanger 17 is not provided, and the refrigerant fromthe expansion valve 6 of the first heat pump 2 is passed through thefirst evaporator 7, the second evaporator 8 and the third sub-heatexchanger 16 in sequence, and is fed to the compressor 4.

In any order of distribution of the refrigerant in the first heat pump2, basically, it is preferred that the first evaporator 7 and the secondevaporator 8 are provided on the upstream side of the third sub-heatexchanger 16 and the fourth sub-heat exchanger 17.

As described above, the steam generation system 1 according to thisembodiment employs, for example, a drain as the heat source fluid. Inone example, a drain at 158° C. is supplied to the second evaporator 8of the first heat pump 2, and is discharged at 125° C. Thereafter, thedrain is supplied to the evaporator 12 of the second heat pump 3, and isdischarged at 80° C. In the second heat pump 3, the temperature of therefrigerant is changed to 75° C. on the low-temperature side (the inletside of the compressor 9). In the first heat pump 2, the temperature ofthe refrigerant is changed to 120° C. on the low-temperature side (theinlet side of the compressor 4), and is changed to 163° C. on thehigh-temperature side (the outlet side of the compressor 4). In thecondenser 5, steam at 158° C. is generated.

In the steam generation system 1 according to this embodiment, the heatsource fluid is passed through the second evaporator 8 of the first heatpump 2, and then is passed through the evaporator 12 of the second heatpump 3. Thus, even when the drain is cooled in the second evaporator 8of the first heat pump 2, the second heat pump 3 makes up for the drawnheat, thereby drawing heat again from the drain passed through thesecond evaporator 8. Moreover, the first heat pump 2 is capable ofreducing the temperature difference in heat to be drawn, reducingelectric power for the compressor 4 in accordance with the reduceddifference, and improving the efficiency of the steam generation system1.

In other words, the steam generation system 1 seems to include theplurality of heat pumps 2 and 3 (two heat pumps in this embodiment) as awhole, and draws a part (typically, half) of energy from the middle heatpump, thereby increasing a coefficient of performance. Moreover, thesteam generation system 1 is capable of reducing energy to be drawn fromthe lowermost heat pump (typically, into halves), and therefore iscapable of reducing the capacity of the compressor 9 in the lower heatpump (i.e., of the second heat pump 3).

FIG. 4 is a graph illustrating a comparison between the steam generationsystem 1 according to this embodiment and a conventionally well-knowntwo-stage heat pump in terms of a coefficient of performance. In FIG. 4,a solid line indicates the steam generation system 1 according to thisembodiment, and a broken line indicates the conventionally well-knowntwo-stage heat pump. FIG. 4 illustrates a case where a drain is used asthe heat source fluid, the horizontal axis indicates a final draintemperature after the drain is passed through the evaporator 12 of thesecond heat pump 3, and the vertical axis indicates a theoreticalcoefficient of performance. A refrigerant used herein is R-365mfc, andconsideration is given to the conditions described above, i.e., the casewhere the drain having the initial temperature of 158° C. is used forgenerating steam at 158° C. (5 kgf/cm² (G)).

As illustrated in FIG. 4, the steam generation system 1 according tothis embodiment operates with higher efficiency as compared with theconventionally well-known two-stage heat pump, irrespective of thetemperature of the heat source fluid (drain). Herein, the conventionallywell-known two-stage heat pump has a configuration equal to theconfiguration that the second evaporator 8 is not provided and heat isdrawn from only the evaporator 12 of the lowermost second heat pump 3 inFIG. 1.

FIG. 5 is a graph illustrating a comparison between the steam generationsystem 1 according to this embodiment and the conventionally well-knowntwo-stage heat pump in terms of a compressor intake volume flow rate ineach of the upper and lower heat pumps. In FIG. 5, a solid lineindicates the steam generation system 1 according to this embodiment,and a broken line indicates the conventionally well-known two-stage heatpump. FIG. 5 illustrates a case where a drain is used as the heat sourcefluid, the horizontal axis indicates a final drain temperature after thedrain is passed through the evaporator 12 of the second heat pump 3, andthe vertical axis indicates a compressor intake volume flow rate.

As illustrated in FIG. 5, the steam generation system 1 according tothis embodiment is capable of reducing the compressor intake volume flowrate, irrespective of the temperature of the heat source fluid (drain).Accordingly, the steam generation system 1 according to this embodimentoperates with higher coefficient as compared with the conventionallywell-known two-stage heat pump.

FIG. 6A is a T-S diagram in a case of ideally drawing heat (hereinafter,referred to as an ideal cycle) under conditions of saturated water inwhich a state of the fluid receiving heat at the inlet is T_(h),saturated steam in which a state of the fluid receiving heat at theoutlet is T_(h) (i.e., sensible heat is given to the fluid receivingheat), saturated water in which a state of the fluid giving heat at theinlet is T_(h), and supercooled water in which a state of the fluidgiving heat at the outlet is T₁ (i.e., sensible heat is drawn from thefluid giving heat). Herein, the vertical axis indicates a temperature,and the horizontal axis indicates entropy.

The area of a triangle enclosed with this ideal cycle, i.e., a solidline corresponds to a minimum power (ideal power) for realizing theconditions described above. A coefficient of performance COP at thistime is obtained as follows:

COP=2×(T _(h)/(T _(h) −T ₁)).

On the other hand, FIG. 6B is a T-S diagram of a conventionallywell-known single-stage heat pump (inverse Carnot cycle). However, FIG.6B illustrates a case where losses at the outlet of the expansion valveand losses by overheat of the compressor are ignored so that heatexchange performance becomes infinite. In this case, the coefficient ofperformance COP is obtained as follows: COP=T_(h)/(T_(h)−T₁). Thesimilar things may hold true for the case where the heat pump isconfigured with a two-stage heat pump in which two heat pumps arevertically disposed, as shown with a chain double-dashed line A.

It is apparent from a comparison between FIG. 6A and FIG. 6B that apower derived by subtracting the area of a triangle in FIG. 6A from thearea of a square in FIG. 6B corresponds to an extra power relative tothe ideal cycle, and the coefficient of performance decreases inaccordance with this extra power.

On the other hand, FIG. 7 is a T-S diagram of the steam generationsystem according to this embodiment. In this case, the coefficient ofperformance COP is obtained as follows: COP=(4/3)×(T_(h)/(T_(h)−T₁)).That is, the efficiency of the steam generation system 1 is 4/3 times aslarge as that of the conventionally well-known single-stage heat pump.Herein, the following relations are established: t_(m)=(t_(h)+t₁)/2 andS_(m)=(S₁+S₂)/2. As compared with FIG. 6B, the right bottom portion canbe eliminated, so that the efficiency can be improved since the powercorresponding to this eliminated portion is reduced.

In the example illustrated in FIG. 7, the number of heat pumps is two.When the number of heat pumps is increased, an area to be enclosed witha cycle can be further reduced as illustrated in FIG. 8, so that theefficiency of the steam generation system 1 can be further improved.When the number of heat pumps is set infinite, the following relation istheoretically established: COP=2×(T_(h)/(T_(h)−T₁)). That is, theefficiency of the steam generation system 1 can be made twice as largeas that of the conventionally well-known single-stage heat pump. Aspecific configuration of the steam generation system 1 in which thenumber of heat pumps is increased will be described later.

Second Embodiment

FIG. 9 is a schematic diagram illustrating a steam generation system 1according to a second embodiment of the present invention. The steamgeneration system 1 according to the second embodiment is basicallysimilar to that according to the first embodiment. In the following,therefore, differences between the first and second embodiments will bemainly described with the corresponding components denoted with the samereference sign.

The second embodiment is different from the first embodiment in aconfiguration of connection between a first heat pump 2 and a secondheat pump 3. In the first embodiment, the first heat pump 2 and thesecond heat pump 3 are connected via the indirect heat exchanger 13. Inthe second embodiment, on the other hand, the first heat pump 2 and thesecond heat pump 3 are connected via an intermediate cooler 18.

Specifically, the intermediate cooler 18 receives a refrigerant from acompressor 9 of the second heat pump 3 and a refrigerant from anexpansion valve 6 of the first heat pump 2, and brings both therefrigerants into direct contact with each other to perform heatexchange. The intermediate cooler 18 serves as a condenser 10 of thesecond heat pump 3 and an evaporator 7 of the first heat pump 2. Morespecifically, the intermediate cooler 18 is a hollow tank (direct heatexchanger) that receives the refrigerant from the compressor 9 of thesecond heat pump 3 and the refrigerant from the expansion valve 6 of thefirst heat pump 2 and brings both the refrigerants into direct contactwith each other in the tank, thereby condensing the refrigerant from thecompressor 9 of the second heat pump 3 and evaporating the refrigerantfrom the expansion valve 6 of the first heat pump 2. Then, theintermediate cooler 18 feeds a liquid refrigerant obtained as describedabove to an expansion valve 11 of the second heat pump 3, and feeds agas-liquid mixed refrigerant to the compressor 4 via a second evaporator8 of the first heat pump 2.

In the second embodiment, the refrigerant from the expansion valve 6 ofthe first heat pump 2 is basically fed to the compressor 4 via theintermediate cooler 18 and the second evaporator 8 in sequence. Sincethe refrigerant is boiled also in the second evaporator 8, therefrigerant to be fed from the intermediate cooler 18 to the secondevaporator 8 contains a vapor phase and a liquid phase in apredetermined mixing ratio. The mixing ratio is adjusted by, forexample, adjusting the apertures of valves (not illustrated) provided ona refrigerant channel for the vapor phase and a refrigerant channel forthe liquid phase from the intermediate cooler 18, respectively.

In the second embodiment, a third sub-heat exchanger 16 is not provided.The other configurations are similar to those in the first embodiment;therefore, the description thereof will not be given here.

Next, description will be given of a modification example of the steamgeneration system 1 according to the second embodiment. In themodification example, differences from FIG. 9 will be mainly described,and the similar configurations will not be described here. In thefollowing description, moreover, corresponding components are denotedwith the same reference sign.

FIG. 10 is a schematic diagram illustrating the modification example ofthe steam generation system 1 according to the second embodiment. In thesteam generation system 1 illustrated in FIG. 9, the refrigerant fromthe compressor 9 of the second heat pump 3 is supplied to theintermediate cooler 18. In this modification example, on the other hand,as shown with a chain double-dashed line A, the refrigerant is suppliedto a refrigerant channel from the intermediate cooler 18 to thecompressor 4 in the first heat pump 2, in place of or in addition to thesupply to the intermediate cooler 18. Herein, the channel shown with thechain double-dashed line A may be connected to either an inlet side oran outlet side of the second evaporator 8. Alternatively, in a casewhere a fourth sub-heat exchanger 17 is provided, the channel may beconnected to either an inlet side or an outlet side of the fourthsub-heat exchanger 17. Further, as shown with a chain double-dashed lineB, the refrigerant from the compressor 9 of the second heat pump 3 maybe flown into a refrigerant channel from the expansion valve 6 to theintermediate cooler 18 in the first heat pump 2.

Third Embodiment

FIG. 11 is a schematic diagram illustrating a steam generation system 1according to a third embodiment of the present invention. The steamgeneration system 1 according to the third embodiment is basicallysimilar to that according to the first embodiment. In the following,therefore, differences between the first and third embodiments will bemainly described with the corresponding components denoted with the samereference sign.

The third embodiment is different from the first embodiment in aconfiguration of connection between a first heat pump 2 and a secondheat pump 3. In the first embodiment, the first heat pump 2 and thesecond heat pump 3 are connected via the indirect heat exchanger 13. Inthe third embodiment, on the other hand, the first heat pump 2 and thesecond heat pump 3 are connected via an intermediate cooler 19.

Specifically, the intermediate cooler 19 receives a refrigerant from acompressor 9 of the second heat pump 3 and a refrigerant from anexpansion valve 6 of the first heat pump 2 to perform heat exchange bybringing both the refrigerants into direct contact with each other andalso to perform heat exchange without mixing both the refrigerants witha refrigerant to be supplied from a condenser 5 of the first heat pump 2to an expansion valve 11 of the second heat pump 3 without being passedthrough expansion valve 6. The intermediate cooler 19 serves as acondenser 10 of the second heat pump 3 and an evaporator 7 of the firstheat pump 2. More specifically, the intermediate cooler 19 is anindirect heat exchanger that performs heat exchange without mixing afluid in a first region 20 with a fluid in a second region 21. Therefrigerant from the compressor 9 of the second heat pump 3 and therefrigerant from the expansion valve 6 of the first heat pump 2 aredirectly subjected to heat exchange in the first region 20. On the otherhand, the refrigerant is passed from the condenser 5 of the first heatpump 2 to the second region 21 without being passed through theexpansion valve 6, and then is supplied to the expansion valve 11 of thesecond heat pump 3. In this case, the refrigerant from the compressor 9of the second heat pump 3 is subjected to intermediate cooling using therefrigerant from the expansion valve 6 of the first heat pump 2, in theintermediate cooler 19. Then, the refrigerant is changed to ahigh-pressure, high-temperature gaseous refrigerant in the compressor 4of the first heat pump 2, and is condensed in the condenser 5 of thefirst heat pump 2. A part of the liquid refrigerant is fed to the firstregion 20 of the intermediate cooler 19 via the expansion valve 6 of thefirst heat pump 2. On the other hand, the remaining liquid refrigerantis decompressed in the expansion valve 11 of the second heat pump 2 viathe second region 21 of the intermediate cooler 19, and is evaporated inthe evaporator 12 of the second heat pump 3. Thereafter, the gaseousrefrigerant is returned to the compressor 9 of the second heat pump 3again.

With this configuration, the third sub-heat exchanger 16 is not providedin the third embodiment. The other configurations are similar to thosein the first embodiment; therefore, the description thereof will not begiven here.

Next, description will be given of a modification example of the steamgeneration system 1 according to the third embodiment. In themodification example, differences from FIG. 11 will be mainly described,and the similar configurations will not be described. In the followingdescription, moreover, corresponding components are denoted with thesame reference sign.

FIG. 12 is a schematic diagram illustrating the modification example ofthe steam generation system 1 according to the third embodiment. In thesteam generation system 1 illustrated in FIG. 11, the refrigerant fromthe compressor 9 of the second heat pump 3 is supplied to theintermediate cooler 19. In this modification example, on the other hand,as shown with a chain double-dashed line A, the refrigerant is suppliedto a refrigerant channel from the intermediate cooler 19 to thecompressor 4 in the first heat pump 2, in place of or in addition to thesupply to the intermediate cooler 19. Herein, the channel shown with thechain double-dashed line A may be connected to either an inlet side oran outlet side of the second evaporator 8. Alternatively, in a casewhere a fourth sub-heat exchanger 17 is provided, the channel may beconnected to either an inlet side or an outlet side of the fourthsub-heat exchanger 17. Further, as shown with a chain double-dashed lineB, the refrigerant from the compressor 9 of the second heat pump 3 maybe supplied to a refrigerant channel from the expansion valve 6 to theintermediate cooler 19 in the first heat pump 2. Herein, in a case wherea separator 22 to be described later is provided on the refrigerantchannel from the expansion valve 6 to the intermediate cooler 19 in thefirst heat pump 2, the refrigerant may be supplied to a refrigerantchannel from the expansion valve 6 to the separator 22. Alternatively, avapor-phase refrigerant from the separator 22 may be supplied to arefrigerant channel 23.

In this modification example, further, the separator 22 is provided onthe outlet side of the expansion valve 6 of the first heat pump 2. Inthis case, a liquid-phase refrigerant separated by the separator 22 issupplied to the intermediate cooler 19, and the vapor-phase refrigerantis supplied to the channel 23, i.e., the refrigerant channel from theintermediate cooler 19 to the compressor 4 in the first heat pump 2.Herein, the channel 23 may be connected to either the inlet side or theoutlet side of the second evaporator 8. Alternatively, in the case wherethe fourth sub-heat exchanger 17 is provided, the channel 23 may beconnected to either the inlet side or the outlet side of the fourthsub-heat exchanger 17.

In place of or in addition to the provision on the refrigerant channelfrom the expansion valve 6 to the intermediate cooler 19 in the firstheat pump 2, the separator 22 may be provided on the refrigerant channelfrom the intermediate cooler 19 to the second evaporator 8. In thiscase, the liquid-phase refrigerant may be supplied to the secondevaporator 8, and the vapor-phase refrigerant may be supplied to anyposition on the refrigerant channel from the second evaporator 8 to thecompressor 4.

Fourth Embodiment

FIG. 13 is a schematic diagram illustrating a steam generation system 1according to a fourth embodiment of the present invention. The steamgeneration system 1 according to the fourth embodiment is basicallysimilar to that according to the first embodiment. In the following,therefore, differences between the first and fourth embodiments will bemainly described with the corresponding components denoted with the samereference sign.

In the first embodiment, the first evaporator 7 and the secondevaporator 8 are provided in series. In the fourth embodiment, on theother hand, a first evaporator 7 and a second evaporator 8 are providedin parallel. That is, in this embodiment, a refrigerant from anexpansion valve 6 of a first heat pump 2 is supplied to a compressor 4via the first evaporator 7 and a third sub-heat exchanger 16 to beprovided as desired, and is also supplied to the compressor 4 via thesecond evaporator 8 and a fourth sub-heat exchanger 17 to be provided asdesired.

FIG. 14 is a diagram illustrating order of distribution of therefrigerant in the first heat pump 2 to the first evaporator 7 of thefirst heat pump 2, and the third sub-heat exchanger 16 to be provided asdesired, and also illustrating order of distribution of the refrigerantin the first heat pump 2 to the second evaporator 8 of the first heatpump 2, and the fourth sub-heat exchanger 17 to be provided as desired,in the fourth embodiment. Numerals in FIG. 14 each indicate the order ofdistribution to the respective heat exchangers 7, 16, 8 and 17, and “0”indicates that the relevant heat exchanger is not provided. The heatexchangers indicated by the same numeral are provided in parallel.

Some specific examples will be described below. For example, “1”, “2”,“1” and “2” are shown in the first row. Herein, the first evaporator 7corresponds to “1”, the third sub-heat exchanger 16 corresponds to “2”,the second evaporator 8 corresponds to “1”, and the fourth sub-heatexchanger 17 corresponds to “2”. In this case, the refrigerant from theexpansion valve 6 of the first heat pump 2 is passed through arefrigerant channel from the first evaporator 7 to the third sub-heatexchanger 16 and a refrigerant channel from the second evaporator 8 tothe fourth sub-heat exchanger 17 in parallel, and then is fed to thecompressor 4.

Moreover, “1”, “2”, “1” and “3” are shown in the second row. Herein, thefirst evaporator 7 corresponds to “1”, the third sub-heat exchanger 16corresponds to “2”, the second evaporator 8 corresponds to “1”, and thefourth sub-heat exchanger 17 corresponds to “3”. In this case, therefrigerant from the expansion valve 6 of the first heat pump 2 ispassed through the first evaporator 7 and the second evaporator 8 inparallel, is passed through the third sub-heat exchanger 16 and thefourth sub-heat exchanger 17 in sequence, and then is fed to thecompressor 4. Alternatively, the refrigerant from the expansion valve 6of the first heat pump 2 is passed through the first evaporator 7 andthe third sub-heat exchanger 16 in sequence, and is passed through thesecond evaporator 8 in parallel therewith. Thereafter, the tworefrigerators are merged, and the merged refrigerant is fed to thecompressor 4 via the fourth sub-heat exchanger 17.

Moreover, “1”, “0”, “1” and “1” are shown in the fourth row. Herein, thefirst evaporator 7 corresponds to “1”, the third sub-heat exchanger 16corresponds to “0”, the second evaporator 8 corresponds to “1”, and thefourth sub-heat exchanger 17 corresponds to “1”. In this case, the thirdsub-heat exchanger 16 is not provided, and the refrigerant from theexpansion valve 6 of the first heat pump 2 is passed through the firstevaporator 7, the second evaporator 8 and the fourth sub-heat exchanger17 in parallel, and then is fed to the compressor 4.

In any order of distribution of the refrigerant in the first heat pump2, basically, it is preferred that the first evaporator 7 and the secondevaporator 8 are provided on the upstream side of the third sub-heatexchanger 16 and the fourth sub-heat exchanger 17. The otherconfigurations are similar to those in the first embodiment; therefore,the description thereof will not be given here.

Fifth Embodiment

FIG. 15 is a schematic diagram illustrating a steam generation system 1according to a fifth embodiment of the present invention. The steamgeneration system 1 according to the fifth embodiment is basicallysimilar to that according to the second embodiment. In the following,therefore, differences between the fifth and second embodiments will bemainly described with the corresponding components denoted with the samereference sign.

In the second embodiment, the vapor-phase refrigerant and theliquid-phase refrigerant are supplied in the predetermined mixing ratiofrom the intermediate cooler 18 to the compressor 4 via the secondevaporator 8 and the fourth sub-heat exchanger 17 to be provided asdesired. In the fifth embodiment, on the other hand, a refrigerantchannel connecting between a vapor-phase part of an intermediate cooler18 and a compressor 4 and a refrigerant channel connecting between aliquid phase part of the intermediate cooler 18 and the compressor 4 areprovided in parallel. Moreover, a second evaporator 8 and a fourthsub-heat exchanger 17 to be provided as desired are provided on thelatter refrigerant channel. Herein, the vapor-phase refrigerant from theintermediate cooler 18 is directly supplied to the inlet side of thecompressor 4. Additionally, in the case where the fourth sub-heatexchanger 17 is provided, the vapor-phase refrigerant from theintermediate cooler 18 may be supplied to the upstream side of thecompressor 4 as shown with a chain double-dashed line A.

The relation between the fourth and fifth embodiments corresponds to therelation between the first and second embodiments. The otherconfigurations are similar to those in the second embodiment; therefore,the description thereof will not be given here.

Next, description will be given of a modification example of the steamgeneration system 1 according to the fifth embodiment. In themodification example, differences from FIG. 15 will be mainly described,and the similar configurations will not be described. In the followingdescription, moreover, corresponding components are denoted with thesame reference sign.

FIG. 16 is a schematic diagram illustrating the modification example ofthe steam generation system 1 according to the fifth embodiment. In thesteam generation system 1 illustrated in FIG. 15, the refrigerant fromthe compressor 9 of the second heat pump 3 is supplied to theintermediate cooler 18. In this modification example, on the other hand,the refrigerant is supplied to a vapor-phase refrigerant channel fromthe intermediate cooler 18 to the compressor 4 as shown with a chaindouble-dashed line A, or supplied to a liquid-phase refrigerant channelfrom the intermediate cooler 18 to the compressor 4 as shown with achain double-dashed line B, in place of or in addition to the supply tothe intermediate cooler 18. In the latter case, the channel shown withthe chain double-dashed line may be connected to either the inlet sideor the outlet side of the second evaporator 8. Alternatively, in thecase where the fourth sub-heat exchanger 17 is provided, the channel maybe connected to either the inlet side or the outlet side of the fourthsub-heat exchanger 17. Further, as shown with a chain double-dashed lineC, the refrigerant from the compressor 9 of the second heat pump 3 maybe flown into the refrigerant channel from the expansion valve 6 to theintermediate cooler 18 in the first heat pump 2.

Sixth Embodiment

FIG. 17 is a schematic diagram illustrating a steam generation system 1according to a sixth embodiment of the present invention. The steamgeneration system 1 according to the sixth embodiment is basicallysimilar to that according to the third embodiment. In the following,therefore, differences between the sixth and third embodiments will bemainly described with the corresponding components denoted with the samereference sign.

In the third embodiment, the refrigerant from the expansion valve 6 ofthe first heat pump 2 is supplied to the compressor 4 via theintermediate cooler 19 and the second evaporator 8. In the sixthembodiment, on the other hand, a refrigerant from an expansion valve 6of a first heat pump 2 is supplied to a compressor 4 via an intermediatecooler 19, but is not passed through a second evaporator 8. In paralleltherewith, the refrigerant is supplied to the compressor 4 via thesecond evaporator 8, but is not passed through the intermediate cooler19.

As shown with a chain double-dashed line A, the refrigerant suppliedfrom the expansion valve 6 of the first heat pump to the intermediatecooler 19 may be merged with a refrigerant supplied from a compressor 9of a second heat pump 3 to the intermediate cooler 19. As shown with achain double-dashed line X, moreover, the refrigerant from theintermediate cooler 19 to the compressor 4 may be supplied forward of afourth sub-heat exchanger 17 in some cases.

The relation between the fourth and sixth embodiments corresponds to therelation between the first and third embodiments. The otherconfigurations are similar to those in the third embodiment; therefore,the description thereof will not be given here.

Next, description will be given of a modification example of the steamgeneration system 1 according to the sixth embodiment. In themodification example, differences from FIG. 17 will be mainly described,and the similar configurations will not be described. In the followingdescription, moreover, the corresponding components are denoted with thesame reference sign.

FIG. 18 is a schematic diagram illustrating a first modification exampleof the steam generation system 1 according to the sixth embodiment. Inthe steam generation system 1 illustrated in FIG. 17, the refrigerantfrom the compressor 9 of the second heat pump 3 is supplied to theintermediate cooler 19. In this modification example, on the other hand,the refrigerant may be flown into the refrigerant channel from theexpansion valve 6 to the intermediate cooler 19 in the first heat pump 2as shown with a chain double-dashed line A, may be supplied to therefrigerant channel from the expansion valve 6 to the compressor 4 viathe second evaporator 8 as shown with a chain double-dashed line B, ormay be supplied to the refrigerant channel from the intermediate cooler19 to the compressor 4 as shown with a chain double-dashed line C, inplace of or in addition to the supply to the intermediate cooler 19.

FIG. 19 is a schematic diagram illustrating a second modificationexample of the steam generation system 1 according to the sixthembodiment. In this embodiment, a separator 22 (22A to 22C) is providedon the outlet side of the expansion valve 6 of the first heat pump 2.The refrigerant from the expansion valve 6 of the first heat pump 2 isbranched to a channel 25 to the second evaporator 8 and a channel 26 tothe intermediate cooler 19 via a common channel 24. The separator 22 maybe provided at any position on the channels. The separator to beprovided on the common channel 24 corresponds to the first separator22A, the separator to be provided on the channel 25 to the secondevaporator 8 corresponds to the second separator 22B, and the separatorto be provided on the channel 26 to the intermediate cooler 19corresponds to the third separator 22C. These separators can be providedby a combination illustrated in FIG. 20. In FIG. 20, “1” indicates thatthe separator is provided, and “0” indicates that the separator is notprovided.

In FIG. 20, the pattern in the first row indicates that no separatorsare provided. The pattern in the second row indicates that only thefirst separator 22A is provided. In this case, the liquid-phaserefrigerant separated by the separator 22A is supplied to theintermediate cooler 19 and the second evaporator 8, and the vapor-phaserefrigerant is supplied to any position from the second evaporator 8 tothe compressor 4 as shown with the chain double-dashed line A.

Moreover, the pattern in the third row indicates that only the secondseparator 22B is provided. In this case, the refrigerant from theexpansion valve 6 of the first heat pump 2 is supplied to theintermediate cooler 19 and the separator 22B. The liquid-phaserefrigerant separated by the separator 22B is supplied to the secondevaporator 8, and the vapor-phase refrigerant is supplied to anyposition from the second evaporator 8 to the compressor 4 as shown withthe chain double-dashed line A.

Moreover, the pattern in the fourth row indicates that only the thirdseparator 22C is provided. In this case, the refrigerant from theexpansion valve 6 of the first heat pump 2 is supplied to the secondevaporator 8 and the separator 22C. The liquid-phase refrigerantseparated by the separator 220 is supplied to the intermediate cooler19, and the vapor-phase refrigerant is supplied to any position from thesecond evaporator 8 to the compressor 4 as shown with the chaindouble-dashed line A.

Further, both the second separator 22B and the third separator 22C maybe provided as shown in the pattern in the fifth row. In any cases, theseparator 22 is provided for preventing the vapor-phase refrigerant frombeing supplied to the intermediate cooler 19 and the second evaporator8, so that the heat exchanger that constitutes these components can bemade small.

Seventh Embodiment

FIG. 21 is a schematic diagram illustrating a steam generation system 1according to a seventh embodiment of the present invention. The steamgeneration system 1 according to the seventh embodiment is basicallysimilar to that according to the fourth embodiment. In the following,therefore, differences between the seventh and fourth embodiments willbe mainly described with the corresponding components denoted with thesame reference sign.

In the fourth embodiment, the first evaporator 7 and the secondevaporator 8 are provided in parallel, and the refrigerant passedthrough the common expansion valve 6 is passed through the firstevaporator 7 and the second evaporator 8. In the seventh embodiment, onthe other hand, a refrigerant from a condenser 5 of a first heat pump 2is passed through a refrigerant channel including a first expansionvalve 6A and a first evaporator 7 and a refrigerant channel including asecond expansion valve 6B and a second evaporator 8 in parallel, andthen is supplied to a compressor 4. The other configurations are similarto those in the fourth embodiment; therefore, the description thereofwill not be given here.

Eighth Embodiment

FIG. 22 is a schematic diagram illustrating a steam generation system 1according to an eighth embodiment of the present invention. The steamgeneration system 1 according to the eighth embodiment is basicallysimilar to that according to the fifth embodiment. In the following,therefore, differences between the eighth and fifth embodiments will bemainly described with the corresponding components denoted with the samereference sign.

In the fifth embodiment, the vapor-phase refrigerant channel andliquid-phase refrigerant channel from the intermediate cooler 18 areprovided in parallel, and the refrigerant passed through the commonexpansion valve 6 is passed through the vapor-phase refrigerant channeland the liquid-phase refrigerant channel. In the eighth embodiment, onthe other hand, a refrigerant from a condenser 5 of a first heat pump 2is supplied to an intermediate cooler 18 via a first expansion valve 6Aand, in parallel therewith, is also supplied to a second evaporator 8via a second expansion valve 6B. A vapor-phase part of the intermediatecooler 18 and a compressor 4 are connected to each other via arefrigerant channel. The refrigerant from the second expansion valve 6Bis supplied to the compressor 4 via the second evaporator 8 or a fourthsub-heat exchanger 17 to be provided as desired. The otherconfigurations are similar to those in the fifth embodiment; therefore,the description thereof will not be given here.

Next, description will be given of a modification example of the steamgeneration system 1 according to the eighth embodiment. In themodification example, differences from FIG. 22 will be mainly described,and the similar configurations will not be described here. In thefollowing description, moreover, corresponding components are denotedwith the same reference sign.

FIG. 23 is a schematic diagram illustrating a first modification exampleof the steam generation system 1 according to the eighth embodiment. Inthe steam generation system 1 illustrated in FIG. 22, a refrigerant froma compressor 9 of a second heat pump 3 is supplied to the intermediatecooler 18. In this modification example, on the other hand, therefrigerant may be supplied to the refrigerant channel from theintermediate cooler 18 to the compressor 4 as shown with a chaindouble-dashed line A, or may be supplied to any position on therefrigerant channel from the second expansion valve 6B to the compressor4 via the second evaporator 8 as shown with a chain double-dashed lineB, in place of or in addition to the supply to the intermediate cooler18. Alternatively, the refrigerant from the compressor 9 of the secondheat pump 3 may be merged with the refrigerant from the first expansionvalve 6A of the first heat pump 2, and then may be supplied to theintermediate cooler 18, as shown with a chain double-dashed line C.

FIG. 24 is a schematic diagram illustrating a second modificationexample of the steam generation system 1 according to the eighthembodiment. In this modification example, a separator 22 is provided onthe refrigerant channel from the second expansion valve 6B to the secondevaporator 8. Thus, the refrigerant from the second expansion valve 6Bis separated by the separator 22 into a vapor phase and a liquid phase.Then, the liquid-phase refrigerant is supplied to the second evaporator8, and the vapor-phase refrigerant is supplied to any position on therefrigerant channel from the second evaporator 8 to the compressor 4 asshown with a chain double-dashed line A.

Ninth Embodiment

FIG. 25 is a schematic diagram illustrating a steam generation system 1according to a ninth embodiment of the present invention. The steamgeneration system 1 according to the ninth embodiment is basicallysimilar to that according to the sixth embodiment. In the following,therefore, differences between the ninth and sixth embodiments will bemainly described with the corresponding components denoted with the samereference sign.

In the sixth embodiment, in the first heat pump 2, the refrigerant fromthe common expansion valve 6 is passed through the intermediate cooler19 and second evaporator 8 in parallel, and then is supplied to thecompressor 4. In the ninth embodiment, on the other hand, a refrigerantfrom a condenser 5 of a first heat pump 2 is supplied to an intermediatecooler 19 via a first expansion valve 6A and, in parallel therewith, isalso supplied to a second evaporator 8 via a second expansion valve 6B.The refrigerant from the second expansion valve 6B may be merged with arefrigerant from a compressor 9 of a second heat pump 3 and may besupplied to the intermediate cooler 19 as shown with a chaindouble-dashed line A. The other configurations are similar to those inthe sixth embodiment; therefore, the description thereof will not begiven here.

Next, description will be given of a modification example of the steamgeneration system 1 according to the ninth embodiment. In themodification example, differences from FIG. 25 will be mainly described,and the similar configurations will not be described here. In thefollowing description, moreover, corresponding components are denotedwith the same reference sign.

FIG. 26 is a schematic diagram illustrating a first modification exampleof the steam generation system 1 according to the ninth embodiment. Inthe steam generation system 1 illustrated in FIG. 25, the refrigerantfrom the compressor 9 of the second heat pump 3 is supplied to theintermediate cooler 19. In this modification example, on the other hand,the refrigerant may be flown into a refrigerant channel from the firstexpansion valve 6A to the intermediate cooler 19 as shown with a chaindouble-dashed line A, may be supplied to a refrigerant channel from theintermediate cooler 19 to the compressor 4 as shown with a chaindouble-dashed line B, or may be supplied to any position on arefrigerant channel from the second expansion valve 6B to the compressor4 via the second evaporator 8 as shown with a chain double-dashed lineC, in place of or in addition to the supply to the intermediate cooler19.

FIG. 27 is a schematic diagram illustrating a second modificationexample of the steam generation system 1 according to the ninthembodiment. In this modification example, a first separator 22A isprovided on the refrigerant channel from the second expansion valve 6Bto the second evaporator 8. Accordingly, the refrigerant from the secondexpansion valve 6B is separated by the first separator 22A into a vaporphase and a liquid phase. Then, the liquid-phase refrigerant is suppliedto the second evaporator 8, and the vapor-phase refrigerant is suppliedto any position on the refrigerant channel from the second evaporator 8to the compressor 4 as shown with a chain double-dashed line A. Further,a second separator 22B may be provided on the refrigerant channel fromthe first expansion valve 6A to the intermediate cooler 19. Thus, therefrigerant from the first expansion valve 6A is separated by the secondseparator 22B into a vapor phase and a liquid phase. Then, theliquid-phase refrigerant is supplied to the intermediate cooler 19, andthe vapor-phase refrigerant is supplied to any position on therefrigerant channel from the second evaporator 8 to the compressor 4 asshown with a chain double-dashed line B.

FIG. 28 is a diagram illustrating a combination of layout of the firstseparator 22A and the second separator 22B. In FIG. 28, “1” indicatesthat the separator is provided and “0” indicates that the separator isnot provided. As illustrated in FIG. 28, both the separators 22A and 22Bmay be provided, only one of the separators 22A and 22B may be provided,or none of the separators 22A and 22B may be provided.

Tenth Embodiment

In each of the foregoing embodiments, the first heat pump 2 is asingle-stage heat pump, and the second heat pump 3 is also asingle-stage heat pump. In the respective heat pumps 2 and 3, however,the number of stages can be changed as appropriate. In other words, eachof the foregoing embodiments describes the steam generation system 1that includes two heat pumps as a whole by the combination of thesingle-stage first heat pump 2 and the single-stage second heat pump 3.In the heat pump that constitutes the steam generation system 1,however, the number of stages can be changed as appropriate. Examples ofa multiple-stage heat pump may include a one-way, multiple-stage heatpump as illustrated in FIG. 9, a multiple-way heat pump as illustratedin FIG. 1, and a heat pump obtained by a combination of the two heatpumps.

For example, FIG. 29A illustrates an example that a first heat pump 2 isa two-stage heat pump in which heat pumps are vertically disposed and asecond heat pump 3 is a single-stage heat pump. In other words, a steamgeneration system 1 includes three heat pumps. Herein, the second heatpump 3 may also be a multiple-stage heat pump in which two or more heatpumps are disposed, as in the conventionally well-known two-stage heatpump.

In the steam generation system illustrated in FIG. 29A, except thelowermost heat pump (the second heat pump 3), the respective heat pumps(the heat pumps 2A and 2B in the first heat pump) include firstevaporators 7A and 7B and second evaporators 8A and 8B, respectively, asan evaporator. Each of the first evaporators 7A and 7B connects betweenthe vertically adjoining heat pumps, and a heat source fluid is passedthrough the second evaporators 8A and 8B. Herein, the verticallyadjoining heat pumps may be connected in accordance with any relationdescribed in the foregoing embodiments. More specifically, thevertically adjoining heat pumps are connected via an indirect heatexchanger 13 (13A, 13B) as illustrated in FIG. 29A, but may be connectedvia an intermediate cooler 18, 19 as described above. In the first heatpump 2, the configuration of each heat pump is not limited to thatdescribed in the first embodiment, and each heat pump may be configuredas described in the other embodiments. Typically, the heat source fluidis passed through the respective second evaporators 8 (8A, 8B) insequence from the uppermost heat pump toward the lowermost heat pump.

Preferably, in the case where the steam generation system 1 includesthree or more heat pumps (in other words, in the case where the firstheat pump 2 is a multiple-stage heat pump), except the lowermost heatpump (the second heat pump 3), all the heat pumps 2A and 2B in the firstheat pump 2 include the first evaporators 7A and 7B and the secondevaporators 8A and 8B, respectively, each of the first evaporators 7Aand 7B connects between the vertically adjoining heat pumps, and theheat source fluid is passed through the respective second evaporators 8Aand 8B in sequence from the uppermost heat pump toward the lowermostheat pump.

The reasons why the foregoing configuration is preferable are describedas follows. FIG. 29B is a T-S diagram in a case where the first heatpump 2 is a single-stage heat pump and the second heat pump 3 is atwo-stage heat pump. FIG. 29C is a T-S diagram in a case where the firstheat pump 2 is a two-stage heat pump in which heat pumps include thefirst evaporators 7A and 7B and the second evaporators 8A and 8B,respectively, and the second heat pump 3 is a single-stage heat pump. Acomparison between FIGS. 29B and 29C shows that a hatched areacorresponding to a loss in FIG. 29C can be made smaller than that inFIG. 29B. Therefore, it is preferable that in the steam generationsystem 1, except the lowermost heat pump 3, the first heat pumps 2A and2B include the second evaporators 8A and 8B through which the heatsource fluid is passed.

In the case where the steam generation system 1 includes three or moreheat pumps (in other words, in the case where the first heat pump 2 is amultiple-stage heat pump), if a first sub-heat exchanger 14 is desiredto be provided, the first sub-heat exchanger 14 may be provided on theuppermost heat pump (the uppermost heat pump 2A in the first heat pump2).

Moreover, in the case where the steam generation system 1 includes threeor more heat pumps, if a second sub-heat exchanger 15 is desired to beprovided, the second sub-heat exchanger 15 may be provided on thelowermost heat pump (the lowermost heat pump in the second heat pump 3).

Further, in the case where the steam generation system 1 includes threeor more heat pumps, if a third sub-heat exchanger 16 and/or a fourthsub-heat exchanger 17 are/is desired to be provided, the third sub-heatexchanger 16 and/or the fourth sub-heat exchanger 17 may be provided onthe heat pumps 2A and 2B in the first heat pump 2, respectively. In thiscase, in the lowermost heat pump 2B in the first heat pump 2, the thirdsub-heat exchanger 16 serves as an indirect heat exchanger forperforming heat exchange between a refrigerant from an expansion valve6B of the lowermost heat pump in the first heat pump 2 to a compressor4B and a refrigerant from a compressor 9 of the second heat pump 3 tothe first evaporator 7B. In the upper heat pump 2A in the first heatpump 2, however, the third sub-heat exchanger 16 serves as an indirectheat exchanger for performing heat exchange between a refrigerant froman expansion valve 6A of the upper heat pump 2A to a compressor 4A and arefrigerant from the compressor 4B of the lower first heat pump 2B tothe first evaporator 7A.

FIG. 30 is a schematic diagram illustrating one example of a steamsystem 27 using the steam generation system 1 according to the firstembodiment. For convenience of the description, it is assumed that thesecond evaporator 8 of the first heat pump 2, the fourth sub-heatexchanger 17 to be provided as desired, the evaporator 12 of the secondheat pump 3, and the second sub-heat exchanger 15 to be provided asdesired are each a heat-drawing heat exchanger (8, 17, 12, 15). It isalso assumed that the condenser 5 of the first heat pump 2, and thefirst sub-heat exchanger 14 to be provided as desired are each asteam-generating heat exchanger (5, 14).

The steam system 27 includes the steam generation system 1 and a boiler28. Herein, the steam generation system 1 has the configurationdescribed in the first embodiment, but may be configured as described inthe other embodiments. In any case, the steam generation system 1 drawsheat from a drain in the heat-drawing heat exchanger (8, 17, 12, 15),and generates steam by application of the heat to water in thesteam-generating heat exchanger (5, 14). Thus, a drain from asteam-utilizing facility 29 is passed through the heat-drawing heatexchanger (8, 17, 12, 15). The method of causing the drain pass throughthe respective evaporators 8 and 12 as well as the respective sub-heatexchangers 17 and 15 each serving as the heat-drawing heat exchanger (8,17, 12, 15) is described on the basis of FIG. 2.

On the other hand, a feed pump 30 is operable to supply water to thesteam-generating heat exchanger (5, 14), and the steam-generating heatexchanger (5, 14) is capable of storing a desired amount of water.Specifically, pure water or soft water, or the drain from thesteam-utilizing facility 29 in place thereof or as mixed therewith issupplied to the steam-generating heat exchanger (5, 14) via the feedpump 30, a feed valve 31 and a check valve 32. The method of causingwater or steam pass through the condenser 5 and the first sub-heatexchanger 14 each serving as the steam-generating heat exchanger (5, 14)is also described in the foregoing embodiments.

The boiler 28 is typically a fuel-burning boiler or an electric boiler.The fuel-burning boiler evaporates water by burning fuel. Herein, theexistence/nonexistence and amount of fuel are adjusted such that thesteam pressure is kept at a desired level. The electric boilerevaporates water by means of an electric heater. Herein, thesupply/non-supply and quantity of power to the electric heater areadjusted such that the steam pressure is kept at a desired level. Theboiler 28 can be supplied with water via the feed pump 33 and the checkvalve 34, to keep the water level in the can body of the boiler 28 at adesired level.

A steam path 35 from the steam-generating heat exchanger (5, 14) and asteam path 36 from the boiler 28 are merged with each other. This mergecan be achieved using a steam header. Further, on the steam path 35 fromthe steam-generating heat exchanger (5, 14), a check valve 37 isprovided on the upstream side of the merged portion. Accordingly, steamfrom the boiler 28 is prevented from flowing reverse to thesteam-generating heat exchanger (5, 14) during a halt of the steamgeneration system 1.

Furthermore, on the steam path 36 from the boiler 28, a boiler steamfeed valve 38 is provided on the upstream side of the merged portion.The boiler steam feed valve 38 is assumed to be a self-operateddecompression valve (secondary pressure-regulating valve) in theillustrated example. The upstream side of the boiler steam feed valve 38is kept at a higher pressure than the downstream side by the boiler 28.

Steam from the steam generation system (5, 14) or the boiler 28 is fedto one or more steam-utilizing facilities 29. A drain from thesteam-utilizing facility 29 is discharged into a hollow vessel-shapedseparator tank 40 via a first steam trap 39. The separator tank 40 hasan upper part connected to a first channel 41 and a lower part connectedto a second channel 42.

On the first channel 41, the heat-drawing heat exchangers (8, 17, 12,15) and a second steam trap 43 are provided in sequence from the side ofthe separator tank 40. Because of the configuration described above, thedrain from the steam-utilizing facility 29 is discharged under a lowpressure by the first steam trap 39. Thereafter, the drain is passedthrough the heat-drawing heat exchangers (8, 17, 12, 15), and then isdischarged under a lower pressure (typically, under the atmosphericpressure) by the second steam trap 43. That is, the drain from thesteam-utilizing facility 29 is discharged via the first steam trap 39,so that flash steam and condensed water thereof are obtained. The steamand the condensed water are passed trough the heat-drawing heatexchanger (8, 17, 12, 15) to be cooled (or supercooled), and then aredischarged from the second steam trap 43. In such a configuration, afluid giving heat to a refrigerant in the heat-drawing heat exchanger(8, 17, 12, 15) can be kept at a temperature exceeding 100° C. at apressure exceeding the atmospheric pressure. A drain from the secondsteam trap 43 may be disposed as it is, may be supplied to a feed tank44 for the boiler 28 and/or the steam-generating heat exchanger (5, 14),or may be used as feed water to the steam-generating heat exchanger (5,14) without being passed through the feed tank 44.

On the other hand, a discharge valve 45 is provided on the secondchannel 42. The discharge valve 45 is a self-operated decompressionvalve (primary pressure-regulating valve) in FIG. 30. Because of theconfiguration described above, the drain from the steam-utilizingfacility 29 can be discharged under a low pressure by the first steamtrap 39, and then can be discharged under a lower pressure (typically,under the atmospheric pressure) by the discharge valve 45. The fluidfrom the discharge valve 45 may be disposed as it is, may be supplied tothe feed tank 44 for the boiler 28 and/or the steam-generating heatexchanger (5, 14), or may be used as feed water to the steam-generatingheat exchanger (5, 14) without being passed through the feed tank 44.

For the use in emergency and power failure, preferably, anormally-closed type electromagnetic valve 46 is provided between theseparator tank 40 and the heat-drawing heat exchanger (8, 17, 12, 15) onthe first channel 41, and a normally-open type electromagnetic valve 47is provided in parallel with the discharge valve 45 on the secondchannel 42. In this case, normally, the electromagnetic valve 46 on thefirst channel 41 is kept open and the electromagnetic valve 47 on thesecond channel 42 is kept closed. At the time of emergency or powerfailure, the electromagnetic valve 46 on the first channel 41 is closedand the electromagnetic valve 47 on the second channel 42 is opened.Therefore, the drain from the steam-utilizing facility 29 is dischargedwithout being passed through the heat-drawing heat exchanger (8, 17, 12,15).

The steam-generating heat exchanger (5, 14) is supplied with pure wateror soft water, the drain from the steam-utilizing facility 29, or mixedwater of the drain with the pure water or soft water. A water feedsystem therefor is not particularly limited, but may configured asfollows. The drain from the steam-utilizing facility 29 may be in aliquid phase alone and in a gas-liquid two phase (flash steam andcondensed water thereof generated when the drain at a pressure exceedingthe atmospheric pressure is released under a lower pressure).

(A) As shown with a chain double-dashed line A, a drain comprised of aliquid separated by the separator tank 40 is supplied from the upstreamside of the discharge valve 45 to the inlet side of the feed pump 30.

(B) As shown with a chain double-dashed line B, a drain passed throughthe heat-drawing heat exchanger (8, 17, 12, 15) is supplied from theupstream side of the second steam trap 43 to the inlet side of the feedpump 30. The heat-drawing heat exchanger (8, 17, 12, 15) includes aplurality of heat exchangers. As shown with a chain double-dashed lineB′, however, the drain passed through some of the heat exchangers may bebranched off, and then may be supplied to the inlet side of the feedpump 30.

(C) As shown with a chain double-dashed line C, a drain passed throughthe heat-drawing heat exchanger (8, 17, 12, 15) is supplied from thedownstream side of the second steam trap 43 to the inlet side of thefeed pump 30.

(D) As shown with a broken-line region on the lower side in FIG. 30, adrain from the second steam trap 43 and/or a drain from the dischargevalve 45 are/is stored once in the feed tank 44, and then the water inthis feed tank 44 is supplied to the inlet side of the feed pump 30. Thefeed tank 44 may be supplied with pure water or soft water asappropriate in addition to the drain from the steam-utilizing facility29.

(E) At least two configurations of (A) to (D) above may be combined. Inthis case, at least two supply channels are merged to feed water to thesteam-generating heat exchanger (5, 14). When the feed channels havedifferent inner pressures, the feed pump 30 is not provided on thedownstream side of the merged portion, but may be provided on each ofthe feed channels on the upstream side of the merged portion.

A first sensor 48 which is a pressure sensor is provided at a positionwhere the pressure of a mixture of steam from the steam-generating heatexchanger (5, 14) and steam from the boiler 28 can be detected.Moreover, a second sensor 49 which is a pressure sensor or a temperaturesensor is provided so as to be capable of detecting the pressure ortemperature of the fluid passed through the heat-drawing heat exchanger(8, 17, 12, 15). The steam generation system 1 is controlled on thebasis of values detected by one of or both the first sensor 48 and thesecond sensor 49.

For example, the compressor of the uppermost heat pump (the compressor 4of the first heat pump) may be controlled on the basis of the pressuredetected by the first sensor 48. In addition, the compressor of eachheat pump lower than the uppermost heat pump (the compressor 9 of thesecond heat pump 3) may be controlled on the basis of the pressure ofthe refrigerant in the condenser 10 on the relevant heat pump or theevaporator 7, 8 of the heat pump which is upper by one stage than therelevant heat pump.

Alternatively, the compressor of the lowermost heat pump (the compressor9 of the second heat pump 3) may be controlled on the basis of thepressure or temperature detected by the second sensor 49. In addition,the compressor of each heat pump upper than the lowermost heat pump (thecompressor 4 of the first heat pump 2) may be controlled on the basis ofthe pressure or temperature of the refrigerant in the evaporator 7, 8 ofthe relevant heat pump or the condenser 10 of the heat pump which islower by one stage than the relevant heat pump.

FIG. 31 is a schematic diagram illustrating a modification example ofthe steam system 27 illustrated in FIG. 30. The steam system 27 in FIG.31 is basically similar to that in FIG. 30. In the following, therefore,differences between FIG. 31 and FIG. 30 will be mainly described withthe corresponding components denoted with the same reference sign.

In this modification example, the drain from the steam-utilizingfacility 29 is once stored in a buffer tank 50 serving as a drainreservoir. The drain in the buffer tank 50 can be supplied to theheat-drawing heat exchanger (8, 17, 12, 15) via the first channel 41,and can be discharged via a third channel 51 without being passedthrough the heat-drawing heat exchanger (8, 17, 12, 15).

Specifically, the buffer tank 50 has a lower part connected to the firstchannel 41 and an upper part connected to the third channel 51. On thefirst channel 41, an introduction valve 52, the heat-drawing heatexchanger (8, 17, 12, 15), and the second steam trap 43 are provided insequence from the side of the buffer tank 50. The introduction valve 52is a self-operated decompression valve (secondary pressure-regulatingvalve) in this modification example.

Because of the configuration described above, the drain from thesteam-utilizing facility 29 is discharged under a low pressure by theintroduction valve 52, and then is passed through the heat-drawing heatexchanger (8, 17, 12, 15). Thereafter, the drain is discharged under alower pressure (typically, under the atmospheric pressure) by the secondsteam trap 43. The drain from the second steam trap 43 may be disposedas it is, may be supplied to the feed tank 44 for the boiler 28 and/orthe steam-generating heat exchanger (5, 14), or may be used as feedwater to the steam-generating heat exchanger (5, 14) without beingpassed through the feed tank 44.

On the other hand, a third steam trap 53 is provided on the thirdchannel 51. The third channel 51 is connected to the buffer tank 50 onthe upstream side of the first channel 41, so that the drain overflownfrom the buffer tank 50 is discharged from the third channel 51. Then,the drain is discharged by way of the third steam trap 53. Then, thedrain from the third steam trap 53 may be disposed as it is, may besupplied to the feed tank 44 for the boiler 28 and/or thesteam-generating heat exchanger (5, 14), or may be used as feed water tothe steam-generating heat exchanger (5, 14) without being passed throughthe feed tank 44.

For the use in emergency and power failure, preferably, anormally-closed type electromagnetic valve 46 is provided between theintroduction valve 52 and the buffer tank 50 on the first channel 41. Inthis case, normally, the electromagnetic valve 46 on the first channel41 is kept open. At the time of emergency or power failure, theelectromagnetic valve 46 on the first channel 41 is closed. Therefore,the drain from the steam-utilizing facility 29 is discharged via thethird channel 51 without being passed through the heat-drawing heatexchanger (8, 17, 12, 15).

Also in the case of this modification example, the steam-generating heatexchanger (5, 14) is supplied with pure water or soft water, the drainfrom the steam-utilizing facility, or mixed water of the drain with thepure water or soft water. A water feed system therefor is notparticularly limited, but may configured as follows, as in the caseillustrated in FIG. 30.

(A) As shown with a chain double-dashed line A, the drain from thebuffer tank 50 is supplied from the upstream side of the introductionvalve 52 (any of the upstream side or the downstream side of theintroduction valve 52 in the case where electromagnetic valve 46 isprovided) to the inlet side of the feed pump 30.

(B) As shown with a chain double-dashed line B, a drain passed throughthe heat-drawing heat exchanger (8, 17, 12, 15) is supplied from theupstream side of the second steam trap 43 to the inlet side of the feedpump 30. The heat-drawing heat exchanger (8, 17, 12, 15) includes aplurality of heat exchangers. As shown with a chain double-dashed lineB′, however, the drain passed through some of the heat exchangers may bebranched off, and then may be supplied to the inlet side of the feedpump 30.

(C) As shown with a chain double-dashed line C, a drain passed throughthe heat-drawing heat exchanger (8, 17, 12, 15) is supplied from thedownstream side of the second steam trap 43 to the inlet side of thefeed pump 30.

(D) As shown with a broken-line region on the lower side in FIG. 31, adrain from the second steam trap 43 and/or a drain from the third steamtrap 53 are/is stored once in the feed tank 44, and then the water inthis feed tank 44 is supplied to the inlet side of the feed pump 30. Thefeed tank 44 may be supplied with pure water or soft water asappropriate in addition to the drain from the steam-utilizing facility29. As in the case illustrated in FIG. 30, the feed tank 44 may storethe drain at a pressure exceeding the atmospheric pressure without beingopened upward.

(E) At least two configurations of (A) to (D) above may be combined. Inthis case, at least two supply channels are merged to feed water to thesteam-generating heat exchanger (5, 14). When the feed channels havedifferent inner pressures, the feed pump 30 is not provided on thedownstream side of the merged portion, but may be provided on each ofthe feed channels on the upstream side of the merged portion.

The steam generation system 1 according to the present invention is notlimited to the configurations in the foregoing embodiments and can bechanged as appropriate. For example, the steam generation system 1 isapplied to the steam system 27 illustrated in FIGS. 30 and 31. It goeswithout saying that the steam generation system 1 is applicable to othersystems. In the above description, moreover, the drain from thesteam-utilizing facility 29 is used as the heat source of the steamgeneration system 1; however, the example is not limited to the drain.It is possible to use, for example, exhaust gas from a boiler or thelike, water used to cool the exhaust gas, a hot drain discharged from afactory or the like, water used to cool a compressor, water used ascooling water in an oil cooler for an engine (a drive unit such as acompressor), or water used to cool an engine jacket.

Further, the steam generation system 1 is not limited to the case ofgenerating steam using heat while reducing the temperature of the heatsource fluid. For example, the exhaust steam from the steam-utilizingfacility 29 may be used as the heat source fluid. In this case, theexhaust steam is passed through the fourth sub-heat exchanger 17 and thesecond evaporator 2 in the first heat pump 2 illustrated in FIG. 1.After being passed through the second evaporator 8, the exhaust steammay be decompressed by a steam trap, an orifice or a decompressingvalve, and then may be passed through the second sub-heat exchanger 15and the evaporator 12 in the second heat pump 3. On an exhaust steamchannel, a steam trap or the like may be or may not be provided on theoutlet side of the evaporator 12 of the second heat pump 3. In otherwords, the steam passed through the evaporator 12 of the second heatpump 3 may be in a state exceeding the atmospheric pressure or in theatmospheric state. It goes without saying that one of or both the fourthsub-heat exchanger 17 and the second sub-heat exchanger 15 may beeliminated.

1. A steam generation system comprising: a single-stage ormultiple-stage first heat pump in which at least the lowermost heat pumpincludes a first evaporator and a second evaporator; and a single-stageor multiple-stage second heat pump connected to the first heat pump viaa condenser of the uppermost heat pump, the condenser serving as thefirst evaporator of the lowermost heat pump, wherein a heat source fluidis passed through the second evaporator of the first heat pump and anevaporator of the lowermost heat pump in the second heat pump insequence, and steam is generated by application of heat to water in acondenser of the uppermost heat pump in the first heat pump.
 2. Thesteam generation system of claim 1, wherein the second heat pump is asingle-stage heat pump, heat is drawn from the heat source fluid passedthrough the second evaporator of the first heat pump and the evaporatorof the lowermost heat pump in the second heat pump in sequence, andsteam is generated by application of the heat to water in the condenserof the uppermost heat pump in the first heat pump.
 3. The steamgeneration system of claim 1, wherein the first heat pump is amultiple-stage heat pump in which some of or all of the heat pumps eachinclude the first evaporator and the second evaporator as an evaporator,each of the first evaporators connects between the vertically adjoiningheat pumps, and the heat source fluid is passed through the respectivesecond evaporators in sequence from the upper heat pump toward the towerheat pump.
 4. The steam generation system of claim 3, wherein the heatpumps in the multiple-stage first heat pump each include the firstevaporator and the second evaporator as an evaporator.
 5. The steamgeneration system of claim 1, wherein in the heat pump including thefirst and second evaporators in the single-stage or multiple-stage firstheat pump, the first evaporator and the second evaporator are providedin series or in parallel on a refrigerant channel from an expansionvalve to a compressor, or a first expansion valve and the firstevaporator are provided in parallel with a second expansion valve andthe second evaporator on a refrigerant channel from a condenser to acompressor.
 6. The steam generation system of claim 1, wherein the firstheat pump and the second heat pump are connected in accordance with oneof the following relations (a) to (c): (a) an indirect heat exchanger isprovided for receiving a refrigerant from a compressor of the secondheat pump and a refrigerant from an expansion valve of the first heatpump to perform heat exchange without mixing both the refrigerants, andserves as the condenser of the second heat pump and the first evaporatorof the first heat pump; (b) an intermediate cooler is provided forreceiving a refrigerant from a compressor of the second heat pump and arefrigerant from an expansion valve of the first heat pump to performheat exchange by bringing both the refrigerants into direct contact witheach other, and serves as the condenser of the second heat pump and thefirst evaporator of the first heat pump; and (c) an intermediate cooleris provided for receiving a refrigerant from a compressor of the secondheat pump and a refrigerant from an expansion valve of the first heatpump to perform heat exchange by bringing both the refrigerants intodirect contact with each other and also to perform heat exchange withoutmixing both the refrigerants with a refrigerant to be supplied from thecondenser of the first heat pump to the expansion valve of the secondheat pump without being passed through the expansion valve, and servesas the condenser of the second heat pump and the first evaporator of thefirst heat pump.
 7. The steam generation system of claim 1, wherein whenthe first heat pump and/or the second heat pump are/is a multiple-stageheat pump, the adjoining heat pumps are connected in accordance with oneof the following relations (a) to (c): (a) an indirect heat exchanger isprovided for receiving a refrigerant from a compressor of the lower heatpump and a refrigerant from an expansion valve of the upper heat pump toperform heat exchange without mixing both the refrigerants, and servesas a condenser of the lower heat pump and an evaporator of the upperheat pump; (b) an intermediate cooler is provided for receiving arefrigerant from a compressor of the lower heat pump and a refrigerantfrom an expansion valve of the upper heat pump to perform heat exchangeby bringing both the refrigerants into direct contact with each other,and serves as the condenser of the lower heat pump and the evaporator ofthe upper heat pump; and (c) an intermediate cooler is provided forreceiving a refrigerant from a compressor of the lower heat pump and arefrigerant from an expansion valve of the upper heat pump to performheat exchange by bringing both the refrigerants into direct contact witheach other and also to perform heat exchange without mixing both therefrigerants with a refrigerant to be supplied from the condenser of theupper heat pump to the expansion valve of the lower heat pump withoutbeing passed through the expansion valve, and serves as the condenser ofthe lower heat pump and the evaporator of the upper heat pump.
 8. Thesteam generation system of claim 6, wherein when the first heat pump andthe second heat pump are connected in accordance with the relation (b)in claim 6, the refrigerant from the compressor of the second heat pumpis supplied to a refrigerant channel from the intermediate cooler to thecompressor, in place of or in addition to the supply to the intermediatecooler.
 9. The steam generation system of claim 6, wherein when thefirst heat pump and the second heat pump are connected in accordancewith the relation (c) in claim 6, the refrigerant from the compressor ofthe second heat pump is supplied to a refrigerant channel from theintermediate cooler to the compressor in the first heat pump, or arefrigerant channel from the expansion valve to the intermediate cooleror compressor, in place of or in addition to the supply to theintermediate cooler.
 10. The steam generation system of claim 6, furthercomprising: a separator for separating the refrigerant from theexpansion valve of the first heat pump into a vapor phase and a liquidphase when the first heat pump and the second heat pump are connected inaccordance with the relation (c) in claim 6, wherein the vapor-phaserefrigerant separated by the separator is supplied to a refrigerantchannel from the second evaporator to the compressor.
 11. The steamgeneration system of claim 1, further comprising at least one of: (a) afirst sub-heat exchanger for performing heat exchange between the waterand the refrigerant from the condenser to the expansion valve in theuppermost heat pump of the first heat pump; (b) a second sub-heatexchanger for performing heat exchange between the heat source fluid andthe refrigerant from the evaporator to the compressor in the lowermostheat pump of the second heat pump; (c) a third sub-heat exchanger forperforming heat exchange between the refrigerant from the expansionvalve to the compressor in the lowermost heat pump of the first heatpump and the refrigerant from the compressor to the first evaporator inthe second heat pump, in a case where the first evaporator is anindirect heat exchanger; and (d) a fourth sub-heat exchanger forperforming heat exchange between the heat source fluid and therefrigerant from the expansion valve to the compressor in the lowermostheat pump of the first heat pump, wherein with regard to order ofdistribution of the water and steam to the condenser of the uppermostheat pump in the first heat pump, and the first sub-heat exchanger inthe case where the first sub-heat exchanger is provided, the firstsub-heat exchanger is provided on the upstream side in the case wherethe first sub-heat exchanger is provided, with regard to order ofdistribution of the heat source fluid to the second evaporator of thefirst heat pump, the fourth sub-heat exchanger in the case where thefourth sub-heat exchanger is provided, the evaporator of the lowermostheat pump in the second heat pump, and the second sub-heat exchanger inthe case where the second sub-heat exchanger is provided, the evaporatorof the lowermost heat pump in the second heat pump is provided on thedownstream side, and with regard to order of distribution of therefrigerant to the first evaporator of the first heat pump, the thirdsub-heat exchanger in the case where the third sub-heat exchanger isprovided, the second evaporator of the first heat pump, and the fourthsub-heat exchanger in the case where the fourth sub-heat exchanger isprovided, the first evaporator and the second evaporator are provided onthe upstream side of the third sub-heat exchanger and the fourthsub-heat exchanger.
 12. The steam generation system of claim 1, whereinthe heat source fluid is a drain from a steam-utilizing facility.